Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news about fascinating discoveries, scientific advancements and more.
Meet Retro, the cloned rhesus monkey born on July 16, 2020.
It’s now more than 3 years old and is “doing well and getting stronger,” according to Falong Lu, one of the authors of a study in the journal Nature Communications Tuesday describing how Retro came to be.
Retro is only the second species of primate that scientists have been able to successfully clone. In 2018, the same research team announced that they had made two identical cloned cynomolgus monkeys (a type of macaque) that are still alive today.
“We have obtained the first live and healthy cloned rhesus monkey, which is a huge step forward even though its efficiency is very low compared to normal fertilized embryos, making it impossible,” said Lu, a researcher at the State Key Laboratory. Institute of Molecular Developmental Biology and Genetics and Developmental Biology of the Chinese Academy of Sciences. “Currently, we have not had our second live birth yet.”
The first mammal to be cloned – Dolly the Sheep – was created in 1996 using a technique called somatic cell nuclear transfer, or SCNT; Here, scientists essentially reconstruct an unfertilized egg by fusing a somatic cell nucleus (not from a sperm or egg) with a cell nucleus. egg with the core removed.
Since then, scientists have cloned many mammal species, including pigs, cows, horses and dogs; but the process was hit or miss; Only a small percentage of embryos were transferred to surrogate mothers, resulting in viable offspring.
“After Dolly, we have made some progress in cloning many mammal species, but the reality is that inefficiency remains a major obstacle,” said lead researcher Miguel Esteban of the Guangzhou Institute of Biomedicine and Health in China. Academy of Sciences. He was not involved in the latest research but has collaborated with some members of the research team on other primate studies.
Cloning a rhesus monkey
The Chinese team, based in Shanghai and Beijing, used a modified version of SCNT in their studies on cynomolgus monkeys (Macaca fascicularis) and further developed the technique to clone the rhesus monkey (Macaca mulatta).
During hundreds of unsuccessful cloning attempts, they noticed that the outer membrane that forms the placenta did not develop properly in early cloned embryos. To solve this problem, Esteban explained, they performed a procedure called internal cell mass transplantation, which involves inserting cloned internal cells into a non-cloned embryo, allowing the clone to develop normally.
The team then tested the new technique using 113 reconstructed embryos; 11 of these were transferred to seven surrogate mothers and resulted in only one live birth, according to the study.
“We think there might be additional…. abnormalities to be corrected. Strategies to further increase the success rate of SCNT in primates will continue to be our main focus in the future, Lu said.
The first two cloned monkeys, Zhong Zhong and Hua Hua, are now over 6 years old and living a “happy and healthy life” with other monkeys of the same species. So far, researchers have not identified any potential limits on the lifespan of cloned monkeys, Lu said.
Zhong Zhong and Hua Hua are often described as the first cloned monkeys. However, in 1999, a rhesus monkey was cloned using what researchers considered a simpler cloning method. In this case, instead of using an adult cell, as in the SCNT technique, scientists divide the embryos, as happens naturally when identical twins develop.
Results of monkey cloning
Given that there are limits to what scientists can learn from laboratory mice, successfully cloning monkeys could help speed biomedical research, the researchers said. Research on nonhuman primates closer to humans is vital to life-saving medical advances, including the development of vaccines against Covid-19, according to a report published in May by a panel of the National Academies of Sciences, Engineering, and Medicine. carrying.
The use of monkeys in scientific research is a controversial issue due to ethical concerns regarding animal welfare. The team said it complied with Chinese laws and guidelines governing the use of non-human primates in scientific research.
The UK’s Royal Society for the Prevention of Cruelty to Animals said there were “serious ethical and welfare concerns about the application of cloning technology to animals”. “Cloning animals requires procedures that can cause pain and distress, and there can be high rates of failure and death.”
Being able to produce genetically identical monkeys could be beneficial, Esteban said.
“This research is proof of principle that cloning can be done in different primate species other than humans, and opens the door to new ways to increase efficiency. Cloned monkeys can be genetically edited in complex ways that wild-type monkeys cannot; this has many implications for disease modeling. There is also a species conservation perspective,” he added. .
D., a research scientist at the National Center for Biotechnology (CNB-CSIC) in Spain, who was not involved in the research. Lluís Montoliu said the cloning of both monkey species shows two things.
“First of all, it is possible to clone primates. Secondly, and no less importantly, it is extremely difficult to succeed with these experiments with such low efficiency,” he said.
He added that the low success rate of the process shows that “human cloning would not only be unnecessary and controversial, but would also be extraordinarily difficult and ethically unjustifiable if attempted.”
“Cloning a human being for reproductive purposes is absolutely unacceptable,” Lu said.
For more CNN news and newsletters, create an account at CNN.com